Sheet conveying device and image forming apparatus

ABSTRACT

A sheet conveying device includes a sheet stacking part, a conveying path and a conveying roller. The conveying roller includes a drive roller and a driven roller which is pressed against the drive roller and is driven by the drive roller to be rotated. The drive roller has a rotating drive shaft and a drive roller body rotatable together with the rotating drive shaft. The driven roller has a rotating shaft and a driven roller body supported by the rotating shaft in a rotatable manner. The driven roller body has a plurality of roller parts which are arranged in an axial direction of the rotating shaft and pressed against the drive roller body.

INCORPORATION BY REFERENCE

This application is based on and claims the benefit of priority from Japanese Patent application No. 2016-165727 filed on Aug. 26, 2016, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates to an image forming apparatus including a sheet conveying device configured to convey a sheet.

An image forming apparatus, such as a copying machine and a printer, is provided with a sheet conveying device which conveys a sheet along a sheet conveying path to an image forming part. The sheet conveying device includes a pickup roller and a feed roller. The pickup roller is configured to feed the sheet. The feed roller is configured to separate the fed sheet one by one and then to convey the separated sheet. On the conveying path, a registration roller configured to correct a skew of the sheet fed by the feed roller is provided downstream from the sheet conveying device in the conveying direction.

In addition, depending on a layout of the conveying path, an intermediate roller may be provided between the feed roller and the registration roller in order to assist the sheet for conveying. The conventional intermediate roller includes a rubber made roller and a resin made pulley both of which are pressed each other. In order to obtain a sufficient sheet conveying ability, a nip formed between the roller and the pulley is required to be wide.

By the way, when the resin made pulley may be formed by using a die, the pulley is made to have a difference in outer diameter in its axil direction owing to a draft. The difference in the outer diameter causes a difference in a sheet conveying rate in the axial direction, and thus the sheet may be skewed. The wider the nip between the roller and the pulley is, the greater the degree of the skew is. When one of the intermediate roller is provided between the feed roller and the registration roller, if the degree of the skew is great, the skew may not be corrected by the registration roller. When two to more intermediate rollers are provided, the sheet may be deflected between the intermediate rollers and easily wrinkled.

SUMMARY

In accordance with an aspect of the present disclosure, A sheet conveying device includes a sheet stacking part, a conveying path and a conveying roller. On the sheet stacking part, a sheet is placed. Along the conveying path, the sheet is conveyed. The conveying roller is provided on the conveying path and configured to convey the sheet in a conveying direction along the sheet conveying path. The conveying roller includes a drive roller and a driven roller which is pressed against the drive roller and is driven by the drive roller to be rotated. The drive roller has a rotating drive shaft and a drive roller body rotatable together with the rotating drive shaft. The driven roller has a rotating shaft and a driven roller body supported by the rotating shaft in a rotatable manner. The driven roller body has a plurality of roller parts which are arranged in an axial direction of the rotating shaft and pressed against the drive roller body.

In accordance with an aspect of the present disclosure, an image forming apparatus includes the above described sheet conveying device and an image forming part configured to form an image on the sheet conveyed by the sheet conveying device.

The above and other objects, features, and advantages of the present disclosure will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present disclosure is shown by way of illustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically showing an internal structure of a printer according to one embodiment of the present disclosure.

FIG. 2 is a perspective view showing a part of a sheet conveying device according to one embodiment of the present disclosure.

FIG. 3 is a plan view showing an intermediate roller, in the sheet conveying device according to the embodiment of the present disclosure.

FIG. 4 is a plan view showing a driven roller, in the sheet conveying device according to the embodiment of the present disclosure.

FIG. 5A is a plan view showing a roller body of the driven roller, in the sheet conveying device according to the embodiment of the present disclosure.

FIG. 5B is a plan view showing a first modified example of the roller body of the driven roller, in the sheet conveying device according to the embodiment of the present disclosure.

FIG. 5C is a plan view showing a second modified example of the roller body of the driven roller, in the sheet conveying device according to the embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, with reference to figures, an image forming apparatus and a sheet conveying device according to an embodiment of the present disclosure will be described.

First, with reference to FIG. 1, an entire structure of a printer 1 as an image forming apparatus will be described. FIG. 1 is a view schematically showing the printer 1. In the following description, a near side of a paper plan of FIG. 1 is defined to be a front side of the printer 1, and a right-left direction is defined based on the direction in which the printer 1 is viewed from the front side. Fr, Rr, L and R shown in each figure respectively show the front, rear, left and right sides of the printer 1.

An apparatus main body 2 of the printer 1 includes a sheet conveying device 3 configured to feed a sheet S, an image forming part 6 configured to form a toner image on the fed sheet S, a fixing device 7 configured to fix the toner image to the sheet S, a sheet ejection device 8 configured to eject the sheet S on which the toner image is fixed and an ejection tray 9 on which the ejected sheet S is received.

In the apparatus main body 2, a conveying path 10 along which the sheet S is conveyed is formed so as to extend from the sheet conveying device 4 to the sheet ejection device 8 through the image forming part 6 and the fixing device 7. The conveying path 10 has a curved path 10 a curved upward at about 180° from the sheet conveying device 4 toward image forming part 6. The conveying path 10 extends substantially horizontally from the curved path 10 a to the fixing device 7 through the image forming part 6 and then is curved upward from the fixing device 7 toward the sheet ejection device 8.

Next, with reference to FIG. 1 and FIG. 2, the sheet conveying device 4 will be described. FIG. 2 is a perspective view showing a part of the sheet conveying device. The sheet conveying device 4 includes a sheet stacking part 21 on which a sheet S is placed, a pickup roller 22, a feed roller 23, an intermediate roller 24 and a registration roller 5. The pickup roller 22, the feed roller 23, the intermediate roller 24 as an example of a conveying roller and the registration roller 5 are arranged in the order from the sheet stacking part 21 in a conveying direction along the conveying path 10.

The sheet stacking part 21 is formed into a tray like shape having a size of the sheet S to be placed. On the sheet stacking part 21, a pair of side cursors 31 is supported in a slidable manner in a width direction perpendicular to the conveying direction so as to adjust the sheet S in the width direction. In addition, on the sheet stacking part 21, an end cursor 32 is supported in a slidable manner in the conveying direction so as to adjust a rear edge of the sheet S. Furthermore, on the sheet stacking part 21, a placement plate 33 on which the sheet S is placed is supported in a turnable manner around its upstream side end in the conveying direction. A downstream side end portion of the placement plate 33 in the conveying direction is biased upward by a biasing member (not shown) so that the sheet S placed on the placement plate 33 is kept in an inclined posture in which the downstream side end portion of the sheet S is inclined upward. On a center portion in the width direction of the downstream side end portion of the placement plate 33, a friction pad 34 is attached.

The pickup roller 22 has a rotating shaft 22 a and a roller body 22 b rotatable together with the rotating shaft 22 a.

The pickup roller 22 is supported above the center portion of the downstream side end portion of the placement plate 33 in a rotatable manner. When the placement plate 33 on which the sheet S is placed is inclined into the above described inclined posture, the sheet S is held between the friction pad 34 and the roller body 22 b and then fed to the downstream side by rotation of the rotating shaft 22 a.

The feed roller 23 has a rotating drive shaft 23 a and a feed roller body 23 b rotatable together with the rotating drive shaft 23 a. The feed roller 23 is supported downstream from the pickup roller 22 in the conveying direction at a center portion in the width direction. The rotating drive shaft 23 a is driven by a driving source (not shown) such as a motor to be rotated. The rotating drive shaft 23 a is coupled to the rotating shaft 22 a of the pickup roller 22 via an idle gear or a timing belt. Thus, when the feed roller 23 is rotated in the conveying direction (the counterclockwise direction in FIG. 1), the pickup roller 22 is rotated in the same direction as that of the feed roller 23.

Against the feed roller 23, a separation roller 35 (refer to FIG. 1) is pressed from the lower side to forma separation nip between the feed roller 23 and the separation roller 35. When the feed roller 23 is rotated, the separation roller 35 is driven to be rotated in a reverse direction to the rotating direction of the feed roller 23 so that the sheet S fed to the separation nip is conveyed.

The separation roller 35 stops the rotation until torque of a predetermined value is applied, while being driven by the feed roller 23 to be rotated when torque of the predetermined value or more is applied. When one sheet is fed by the pickup roller 22, because the torque applied to the separation roller 35 is larger than the predetermined value, the separation roller 35 is driven by the feed roller 23 to be rotated and then to convey the sheet S. On the other hand, when a plurality of the sheet S are fed by the pickup roller 22, because the torque applied to the separation roller 35 is smaller than or equal to the predetermined value, the separation roller 35 stops the rotation with the sheet S held between the separation roller 35 andthe feed roller 23 so that the uppermost sheet S is separated from the other lower sheets S and then conveyed to the downstream side by the feed roller 23.

Next, with reference to FIG. 3 and FIG. 4, the intermediate roller 24 will be described. FIG. 3 is a plan view showing a drive roller and a driven roller, and FIG. 4 is a plan view showing the driven roller.

The intermediate roller 24 includes a drive roller 41 disposed on an inner circumference side of the conveying path 10 and a driven roller 42 disposed on an outer circumference side of the conveying path 10, also as shown in FIG. 1. The drive roller 41 and the driven roller 42 are disposed near an apex portion of the curved path 10 a at a center portion in the width direction.

As shown in FIG. 3, the drive roller 41 has a rotating drive shaft 41 a and a drive roller body 41 b rotatable together with the rotating drive shaft 41 a. The drive roller body 41 b is made of rubber, for example, and has a width larger than a width of the feed roller body 23 b of the feed roller 23. The rotating drive shaft 41 a is driven by a drive source (not shown) such as a motor to be rotated.

As shown in FIG. 4, the driven roller 42 has a rotating shaft 51 and a driven roller body 52 supported by the rotating shaft 51 in a rotatable manner. The driven roller body 52 is divided into two roller parts 53 in an axial direction of the rotating shaft 51, and each of the two roller parts 53 is independently rotatable. The two roller parts 53 are identical in shape and size. The two roller parts 53 are arranged in an axial direction of the rotating shaft 51 with a predetermined interval d and restricted from being moved in the axial direction. Preferably, the interval d between the two roller parts 53 is narrow as much as possible. A width W between both outer side ends of the two roller parts 53 is wider than the width of the drive roller body 41 b of the drive roller 41.

With reference to FIG. 5A, the two roller parts 53 will be described. FIG. 5A is a plan view showing shapes and arrangement of the two roller parts.

The two roller parts 53 are made by resin molding using a die. Owing to a draft of the resin molding, each roller part 53 is formed into a truncated cone shape which has a larger diameter end 53 b at one end in the axial direction and a smaller diameter end 53 a at the other end. That is, an outer circumference face of each roller part 53 is inclined so as to be tapered from the larger diameter end 53 b toward the smaller diameter end 53 a. The two roller parts 53 are arranged such that inclined directions of the outer circumference faces are oppose to each other, as shown in FIG. 5A. In detail, the two roller parts 53 are arranged while the smaller diameter ends 53 a facing outward and the larger diameter ends 53 b facing inward.

As shown in FIG. 4, both end portions of the rotating shaft 51 of the driven roller 42 are biased toward the drive roller 41 by coil springs 55. This presses the two roller parts 53 against the drive roller body 41 b of the drive roller 41 to form a nip between the two roller parts 53 and the drive roller body 41 b. The sheet S conveyed to the nip is conveyed to the downstream side by rotation of the drive roller 41.

The registration roller 5 has a drive roller 61 and a driven roller 62 which is pressed against the drive roller 1, as shown in FIG. 1. The drive roller 61 is driven so as to stop the rotation at a predetermined timing. When the drive roller 61 stops the rotation, a front edge of the sheet S abuts against a nip between the drive roller 61 and the driven roller 62

A sheet conveying operation of the sheet conveying device 4 having the above described configuration will be described. The sheet S placed on the placement plate 33 of the sheet stacking part 21 shown in FIG. 2 is adjusted in position in the width direction and the conveying direction by the pair of side cursors 31 and the end cursor 32 respectively. After that, the rotating drive shaft 23 b of the feed roller 23 is driven to rotate the pickup roller 22 and the feed roller 23. Then, the sheet S is fed by the pickup roller 22 to the separation nip between the feed roller 23 and the separation roller 35. At the separation nip, the sheet S is separated one by one as described above, and one sheet S is conveyed to the conveying path 10. The sheet S passed through the separation nip is conveyed to the nip of the intermediate roller 24, and then conveyed to the downstream side by conveying force generated between the drive roller 41 and the driven roller 42.

The two roller parts 53 of the driven roller 42 of the intermediate roller 24 are arranged such that the inclined directions of the outer circumference faces of the two roller parts 53 are different from each other, as shown in FIG. 5A. Thereby, appearance of the skew caused by the difference in the outer diameter of each roller part 53 is canceled so that the sheet S is hardly skewed. Especially, the two roller parts 53 are arranged such that the smaller diameter ends 53 a face outward and the larger diameter ends 53 b face inward. That is, an entire of the two roller parts 53 is formed such that a center portion has a large diameter and both end portions have a small diameter. This makes a conveying rate of the center portion of the sheet S faster. Accordingly, the sheet S is conveyed such that the center portion of the sheet is pulled forward, and wrinkle is hardly generated on the sheet S accordingly.

Additionally, because the drive roller body 41 b of the drive roller 41 has a width wider than that of the feed roller body 23 b of the feed roller 23, sheet powder generatedby friction between the feed roller 23 and the sheet S is hardly passed so that image density unevenness caused by the sheet powder can be prevented. In addition, because the width W between the both outer ends of the two roller parts 53 is wider than the width of the drive roller body 41 b of the drive roller 41, an effect of steps produced on the end portion of the roller part 53 at the resin molding is hardly exerted on the sheet S so that occurrence of a folding line on the sheet S can be prevented.

When the sheet S conveyed by the intermediate roller 24 is conveyed to the registration roller 5, the drive roller 61 of the registration roller 5 stops the rotation. Thereby, a tip edge of the conveyed sheet S abuts against the nip between the drive roller 61 and the driven roller 62. However, because the drive roller 41 of the intermediate roller 24 is rotating, the sheet S is being conveyed by the intermediate roller 24. As a result, the sheet S is deflected until an entire of the tip edge of the sheet S abuts against the nip so that the skew of the sheet S can be corrected. Then, when the drive roller 61 of the registration roller 5 is started the rotation at a suitable timing, the sheet S is conveyed from the nip toward the image forming part 6.

As described above, according to the sheet conveying device 4 of the present disclosure, because the driven roller body 52 of the driven roller 42 of the intermediate roller 24 is formed by the two roller parts 53 each which is independently rotatable, the appearance of the skew of each roller part 53 is distributed so that the skew of the sheet S is hardly occurred. Thereby, the skew can be accurately correctedby the registration roller 5. Accordingly, it becomes possible to convey the sheet S straightly by using a simple configuration.

Additionally, the two roller parts 53 are arranged such that the smaller diameter ends 53 a face outward and the larger diameter ends 53 b face inward, and the entire of the two roller parts 53 is formed such that the center portion has a large diameter and the both end portions have a smaller diameter. This makes a conveying rate of the center portion of the sheet S faster. Accordingly, because the sheet S is conveyed such that the center portion of the sheet S is pulled forward, wrinkle is hardly generated on the sheet S.

Furthermore, the driven roller 42 has the two roller parts 53. This makes the width of each roller part 53 to be narrow. Thereby, the difference in the outer diameter owing the draft becomes small so that the degree of the skew can be reduced.

The two roller parts 53 may be arranged such that the smaller diameter ends 53 a face inward and the larger diameter ends 53 b face outward, as shown in FIG. 5B. Alternately, the two roller parts 53 may be arranged such that the smaller diameter end 53 a of one roller part 53 face the larger diameter end 53 b of the other roller part 53 (such that the inclined directions of the outer circumference faces of the roller parts 53 are made to be the same direction). In these cases, because the roller parts 53 are independently rotated, the appearance of the skew is distributed so that the sheet is hardly skewed. The number of the roller parts 53 may be more than two. The roller part may be made by means other than the resin molding. In this case, if the difference in the outer diameter in the axial direction of the roller part 53 is generated, because the roller parts 53 are independently rotated, the effect of the outer diameter difference is hardly appeared so that the sheet can be conveyed stably.

In the present embodiment, because one of the intermediate roller 24 is arranged between the feed roller 23 and the registration roller 5, the deflection of the sheet S and wrinkling of the sheet S can be reduced. However, depending on layout and length of the conveying path 10 between the feed roller 23 and the registration roller 5, a plurality of the intermediate roller 24 may be arranged.

The pickup roller 22, the feed roller 23, the separation roller 35, the intermediate roller 24 and the registration roller 5 are disposed at the center portion in the width direction so that the sheet S can be conveyed stably regardless of its size.

While the preferable embodiment and its modified example of the sheet conveying device and the image forming apparatus of the present disclosure have been described above and various technically preferable configurations have been illustrated, a technical range of the disclosure is not to be restrictedby the description and illustration of the embodiment. Further, the components in the embodiment of the disclosure may be suitably replaced with other components, or variously combined with the other components. The claims are not restrictedby the description of the embodiment of the disclosure as mentioned above. 

1. A sheet conveying device comprising: a sheet stacking part on which a sheet is placed; a conveying path along which the sheet is conveyed; and a conveying roller provided on the conveying path and configured to convey the sheet in a conveying direction along the sheet conveying path, wherein the conveying roller includes a drive roller and a driven roller which is pressed against the drive roller and is driven by the drive roller to be rotated, the drive roller has a rotating drive shaft and a drive roller body rotatable together with the rotating drive shaft, the driven roller has a rotating shaft and a driven roller body supported by the rotating shaft in a rotatable manner, and the driven roller body has a plurality of roller parts which are arranged in an axial direction of the rotating shaft and pressed against the drive roller body.
 2. The sheet conveying device according to claim 1, wherein each of the plurality of roller parts is independently and rotatably supported on the rotating shaft.
 3. The sheet conveying device according to claim 1, wherein the plurality of rollers are identical in shape and size, each of the plurality of roller parts has a truncated cone shape whose outer circumference face is inclined from a larger diameter end provided at one end in the axial direction toward a smaller diameter end provided at the other end, and the adjacent two roller parts of the plurality of roller parts are arranged in the axial direction such that the inclined directions of the outer circumference faces are different from each other.
 4. The sheet conveying device according to claim 3, wherein the plurality of roller parts includes two of the roller parts adjacently arranged in the axial direction, and the two roller parts are arranged such that the larger diameter end of one of the two roller parts faces the larger diameter end of the other of the two roller parts.
 5. The sheet conveying device according to claim 3, wherein the plurality of roller parts includes two of the roller parts adjacently arranged in the axial direction, and the two roller parts are arranged such that the smaller diameter end of one of the two roller parts faces the smaller diameter end of the other of the two roller parts.
 6. The sheet conveying device according to claim 1, wherein the plurality of rollers are identical in shape and size, each of the plurality of roller parts has a truncated cone shape whose outer circumference face is inclined from a larger diameter end provided at one end in the axial direction toward a smaller diameter end provided at the other end, and the two adjacent roller parts of the plurality of roller parts are arranged in the axial direction such that the inclined directions of the outer circumference faces are made to be the same direction.
 7. The sheet conveying device according to claim 5, wherein the plurality of roller parts includes two of the roller parts adjacently arranged in the axial direction, and the two roller parts are arranged such that the smaller diameter end of one of the two roller parts faces the larger diameter end of the other of the two roller parts.
 8. The sheet conveying device according to claim 1, wherein the driven roller body has a width in the axial direction wider than a width in the axial direction of the drive roller body.
 9. The sheet conveying device according to claim 1, wherein the drive roller body and the driven roller body are disposed at a center portion in a sheet width direction perpendicular to the conveying direction.
 10. The sheet conveying direction according to claim 1, further comprising: a feed roller configured to feed the sheet placed on the sheet stacking part to the conveying path; and a registration roller disposed downstream from the feed roller in the conveying direction and configured to correct a skew of the sheet, wherein the conveying roller is disposed on the conveying path between the feed roller and the registration roller.
 11. The sheet conveying device according to claim 10, wherein the feed roller has a rotating drive shaft and a feed roller body rotatable together with the rotating drive shaft, the feed roller body is disposed at a center portion in a sheet width direction perpendicular to the conveying direction, and the drive roller body has a width in the axial direction wider than a width in the axial direction of the feed roller body.
 12. An image forming apparatus comprising: the sheet conveying device according to claim 1; and an image forming part configured to form an image on the sheet conveyed by the sheet conveying device. 